Bimetal Seleno‐Sulfide CuNiSeS Nanosheet Catalyst for Methylene Blue Degradation in the Dark

In order to overcome the photocatalytic degradation reaction with a need for light excitation, the exploration of a catalyst for the organic degradation reaction without light has become one of the core challenges in catalysis and pollution control. Here we report a novel CuNiSeS nanosheet catalyst with a hexagonal structure by a feasible preparation method. The structure and composition of CuNiSeS were well characterized by X‐ray diffractometry and electron microscopy, and X‐ray photoelectron spectrometry, respectively. The result indicated that the best CuNiSeS‐2 of 25 mg displayed excellent activity even in the dark to complete the degradation of 100 mL of MB solution of 10 ppm within 5 min. This catalyst also showed relatively good stability and durability during the reusability tests. The reasons for the fast MB degradation in the dark were investigated and the reaction kinetic mechanism was proposed. A Cu‐based bimetal seleno–sulfide catalyst system with a CuS covellite structure has been developed for organic degradation that even occurs in the dark. CuNiSeS‐2 showed the fastest degradation of an MB solution (100 mL, 10 ppm) in 5 min, but Ni‐free CuSeS did not have good catalytic activity. The Cu2+/Cu+ ratio, oxygen vacancy, and S6+ are correlated to perform good dye degradation.